Antibiotics worked!!!... then it came back :-(

I had sinusitis in November. Took amoxicillin/clav, which cleared it up. But then it came back in December. So I took another round and it cleared it up again; I was feeling amazing. Until it came back AGAIN. So now, obviously, I'm hesitant to do a third round of antibiotics. But man it felt good to feel good. Anyone had a similar experience?